Why Do Tumbleweeds Tumble?

When we think of a desolate plain or a foreboding frontier town in the wild west, we might think of the iconictumbleweed rolling through the scene. Or they might roll through as a joke. But for people who live in dry parts of western North America, the tumbleweed is, in fact, a weed that can block doors or clog waterways as they gather in piles. They’re neighborhood nuisances that create fire hazards. They also cause accidents when they roll out onto roadways.

Tumbleweeds start out as any plant, attached to the soil. Seedlings, which look like blades of grass with a bright pink stem, sprout at the end of the winter.

By summer, Russian thistle plants take on their round shape and grow white, yellow or pink flowers between thorny leaves. Inside each flower, a fruit with a single seed develops.

Starting in late fall, they dry out and die, their seeds nestled between prickly dried leaves. Gusts of wind easily break dead tumbleweeds from their roots. A microscopic layer of cells at the base of the plant — called the abscission layer — makes a clean break possible and the plants roll away, spreading their seeds. When the rains come, an embryo coiled up inside each seed sprouts.

More related videos

Touch-me-not Balsam pods explode without warning when they're ready to disperse their seeds. The seed pods also happen to be the Netted Carpet Moth larva's favorite food. So what happens when this hungry caterpillar e...

Powered by changes in humidity—curling when dry and straightening when wet—this Erodium cicutarium seed (or more specifically, an achene) will bury itself by slowly drilling into the ground. This time lapse video by p...

Pristine white sand dollars have long been the souvenir to commemorate a successful day at the beach. But most people who pick them up don’t realize that they’ve collected the skeleton of an animal, washed up at the e...

Witness what one commenter calls "a comically absurd amount of tumbleweeds" as they blow across a desert road. The gathering of spiny skeletal balls was captured on a phone cam by Tim Tower while he was driving in Owy...

So. Many. Legs. Thirty legs arranged in a fluttery burst-like arrangement. This is the Scutigera coleoptrata, a house centipede. And though some may think they're creepy or gross, or dangerous to humans (they're not),...

Acorn Woodpeckers eat insects, delicious sap, oak flowers full of pollen... and yes, acorns. They stock up on these bitter but dependable nuts from coast live oaks and California black oaks, storing them in tree trunk...

Normally, an upside-down fish in your tank is bad news. As in, it’s time for a new goldfish.
That’s because most fish have an internal air sac called a swim bladder that allows them to control their buoyancy and or...

See a kidney bean plant germinate, spreading its roots and sprouting up and up with its undulating green leaves, in this time-lapse by YouTuber GPhase. Each shot is captured 9 minutes 36 seconds apart at 30 frames per...

This gigantic flower, native to western Sumatra and infamous for smelling like something rotten, is the corpse flower or titan arum, and it's not really a single flower. The flowers are at the base of the tall spadix ...

Endemic to the Namib Desert, shovel-snouted lizards (Meroles anchietae) have learned how to survive in extreme conditions. They are fast, able to run at over 91.5 cm/3 feet per second. When they rest, they must carefu...

1 year ago

Search & enjoy 4,000+ smart & super-cool, “not-made-for-kids, but perfect for them” videos in the classroom or together at home, curated by Rion Nakaya with her 8 & 10 year olds. Click play and start a conversation.